''Chubutinectes'' (meaning "

Chubut Chubut may refer to: * Chubut Province Chubut ( from Tehuelche language, Tehuelche 'transparent'; ) is a provinces of Argentina, province in southern Argentina, situated between the 42nd parallel south (the border with Río Negro Province), ...

swimmer") is an

extinct Extinction is the termination of an organism by the death of its Endling, last member. A taxon may become Functional extinction, functionally extinct before the death of its last member if it loses the capacity to Reproduction, reproduce and ...

genus of

elasmosaurid Elasmosauridae, often called elasmosaurs or elasmosaurids, is an extinct family of plesiosaurs that lived from the Hauterivian stage of the Early Cretaceous to the Maastrichtian stage of the Late Cretaceous period (c. 130 to 66 mya). The taxo ...

plesiosaur from the

Late Cretaceous The Late Cretaceous (100.5–66 Ma) is the more recent of two epochs into which the Cretaceous Period is divided in the geologic time scale. Rock strata from this epoch form the Upper Cretaceous Series. The Cretaceous is named after ''cre ...

La Colonia Formation The La Colonia Formation is a geological Formation (geology), formation in Argentina whose strata date back to the Late Cretaceous. Dinosaur remains are among the fossils that have been recovered from the formation.Weishampel et al., 2004, pp.600- ...

of Argentina. The genus contains a single species, ''C. carmeloi'', known from a partial skeleton and associated gastroliths.

Discovery and naming

The ''Chubutinectes''

holotype A holotype (Latin: ''holotypus'') is a single physical example (or illustration) of an organism used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of s ...

specimen, MPEF-PV 5232, was discovered in 2009 within sediments of the

on the Somún Curá plateau in

Chubut Province Chubut ( from Tehuelche language, Tehuelche 'transparent'; ) is a provinces of Argentina, province in southern Argentina, situated between the 42nd parallel south (the border with Río Negro Province), the 46th parallel south (bordering Santa ...

, Argentina. The disarticulated specimen consists of cervical, pectoral,

dorsal Dorsal (from Latin ''dorsum'' ‘back’) may refer to: * Dorsal (anatomy), an anatomical term of location referring to the back or upper side of an organism or parts of an organism * Dorsal, positioned on top of an aircraft's fuselage The fus ...

, sacral, and caudal vertebral centra and neural arches, various

rib In vertebrate anatomy, ribs () are the long curved bones which form the rib cage, part of the axial skeleton. In most tetrapods, ribs surround the thoracic cavity, enabling the lungs to expand and thus facilitate breathing by expanding the ...

s, partial

pectoral Pectoral may refer to: * The chest region and anything relating to it. * Pectoral cross, a cross worn on the chest * a decorative, usually jeweled version of a gorget * Pectoral (Ancient Egypt), a type of jewelry worn in ancient Egypt * Pectora ...

and pelvic girdles, fore- and hind-limb elements, and about 350

gastrolith A gastrolith, also called a stomach stone or gizzard stone, is a rock held inside a gastrointestinal tract. Gastroliths in some species are retained in the muscular gizzard and used to grind food in animals lacking suitable grinding teeth. In ...

s. In 2023, O'Gorman and colleagues described ''Chubutinectes carmeloi'' as a new genus and species of

plesiosaur based on these fossil remains. The generic name, "''Chubutinectes''", combines a reference to the Argentinean province "Chubut", where the holotype was found, with the

Greek Greek may refer to: Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group *Greek language, a branch of the Indo-European language family **Proto-Greek language, the assumed last common ancestor of all kno ...

word "nectes", meaning "swimmer". The

specific name Specific name may refer to: * in Database management systems, a system-assigned name that is unique within a particular database In taxonomy, either of these two meanings, each with its own set of rules: * Specific name (botany), the two-part (bino ...

, "''carmeloi''", honors Carmelo Muñoz, the discoverer of the holotype.

Description

The holotype of ''Chubutinectes'' is an osteologically immature specimen with a dorsal region measuring long, indicating that it was larger than an adult ''

Kawanectes ''Kawanectes'' (meaning "Kawas swimmer") is a genus of elasmosauridae, elasmosaurid plesiosaur, a type of long-necked marine reptile, that lived in the marginal marine (probably estuary, estuarine) environment of Late Cretaceous Patagonia. It co ...

'' from the same formation. This size difference may result from their environmental difference, as ''Kawanectes'' lived in

estuaries An estuary is a partially enclosed coastal body of brackish water with one or more rivers or streams flowing into it, and with a free connection to the open sea. Estuaries form a transition zone between river environments and maritime environm ...

, while ''Chubutinectes'' lived in

marine habitat A marine habitat is a habitat that supports marine life. Marine life depends in some way on the seawater, saltwater that is in the sea (the term ''marine'' comes from the Latin ''mare'', meaning sea or ocean). A habitat is an ecological or Na ...

Classification

In their

phylogenetic analyses In biology, phylogenetics () is the study of the evolutionary history of life using observable characteristics of organisms (or genes), which is known as Computational phylogenetics, phylogenetic inference. It infers the relationship among organ ...

, O'Gorman et al. (2023) recovered ''Chubutinectes'' as a member of the elasmosaurid clade

Weddellonectia Elasmosauridae, often called elasmosaurs or elasmosaurids, is an extinct family (biology), family of plesiosaurs that lived from the Hauterivian Stage (stratigraphy), stage of the Early Cretaceous to the Maastrichtian stage of the Late Cretaceou ...

, as the

sister taxon In phylogenetics, a sister group or sister taxon, also called an adelphotaxon, comprises the closest relative(s) of another given unit in an evolutionary tree. Definition The expression is most easily illustrated by a cladogram: Taxon A and ...

to the clade containing '' Aphrosaurus'' and '' Hydrotherosaurus''. Nearly identical results were recovered by O'Keefe et al. (2025) in an updated version of this phylogenetic matrix, the results of which are shown in the

cladogram A cladogram (from Greek language, Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an Phylogenetic tree, evolutionary tree because it does not s ...

below:

Paleoenvironment

''Chubutinectes'' was discovered in layers of the

, which dates to the upper

Maastrichtian The Maastrichtian ( ) is, in the International Commission on Stratigraphy (ICS) geologic timescale, the latest age (geology), age (uppermost stage (stratigraphy), stage) of the Late Cretaceous epoch (geology), Epoch or Upper Cretaceous series (s ...

. Based on the presence of nanofossils of '' Micula'' spp., the rock layers are younger than around 67.3 million years old. The fellow elasmosaurid ''

'' was also found in this formation, as well as the remains of indeterminate elasmosaurids and the polycotylid '' Sulcusuchus''. Dinosaur fossils, including those of the

abelisaurid Abelisauridae (meaning "Abel's lizards") is a family (or clade) of ceratosaurian theropod dinosaurs. Abelisaurids thrived during the Cretaceous period, on the ancient southern supercontinent of Gondwana, and today their fossil remains are foun ...

theropods ''

Carnotaurus ''Carnotaurus'' (; ) is a genus of Theropoda, theropod dinosaur that lived in South America during the Late Cretaceous period, probably sometime between 72 and 69 million years ago. The only species is ''Carnotaurus sastrei''. Known from a si ...

'' and ''

Koleken ''Koleken'' (meaning "coming from clay and water") is a genus of Carnotaurini, carnotaurin abelisaurid from the Maastrichtian La Colonia Formation in the Chubut Province of Argentina. The type and only species is ''K. inakayali'', known from on ...

'',

titanosauria Titanosaurs (or titanosaurians; members of the group Titanosauria) were a diverse group of Sauropoda, sauropod dinosaurs, including genera from all seven continents. The titanosaurs were the last surviving group of long-necked sauropods, with tax ...

n sauropod '' Titanomachya'',

ankylosaurs Ankylosauria is a group of herbivorous dinosaurs of the clade Ornithischia. It includes the great majority of dinosaurs with Armour (zoology), armor in the form of bony osteoderms, similar to turtles. Ankylosaurs were bulky quadrupeds, with short ...

, hadrosauroids, and somphospondylans, have also been found. Other fossils animals include various species of mammals, turtles and snakes.

References

{{Taxonbar, from=Q121354360 Elasmosauridae Fossil taxa described in 2023 Sauropterygian genera Late Cretaceous plesiosaurs Maastrichtian life Plesiosaurs of South America Late Cretaceous reptiles of South America Cretaceous Argentina Fossils of Argentina